The purpose of this research study is to determine the safety and outcome of treatment with an investigational immune globulin product: Immune Globulin Intravenous (Human) manufactured using chromatography as part of the purification process (IGIV-C, 10%) in patients with confirmed Idiopathic (Immune) Thrombocytopenic Purpura (ITP). This condition results in low platelet counts because of increased destruction of platelets (blood cells important for blood clotting) by the body's immune system. Intravenous immune globulin is given to patients with immune thrombocytopenic purpura (ITP) when it is important to raise the level of platelets circulating in the blood stream. Intravenous immune globulin was first licensed for medical use in the United States in 1981, and immune globulin products in various concentrations and from different preparation/purification methods have been licensed for use in the treatment of ITP since then. In this study, Bayer Corporation is evaluating an intravenous immune globulin preparation that is manufactured in a new way. The product is purer than Bayer's prevous preparations of IGIV and more closely reflects the types of immunoglobulin found in normal blood. The manufacturing process also includes a new viral inactivation step that uses a technique called chromatography. The new product will be referred to a IGIV-C, 10%. Although older formulations of Bayer's intravenous immune globulin have been approved for use by the Federal Drug Administration, the new product to be used in this study is not yet approved. Information learned in this study will become part of an application to license this product (IGIV-C, 10%) in the United States and around the world.